| IntroductionLead, as a metallic element, has many applications and is commonly found in home and industrial surroundings. With development of transportation and industry, lead pollution has become more and more serious in our surroundings. Lead is valueless in normal metabolism with a variety of adverse health effects, including auditory functions. Because of children's physiological and metabolic characteristics, they are prone to be lead poisoned, which has become a world public health problem. Overview, current research of lead effects on brainstem auditory evoked potential (BAEP)were just limited in animal experiment and lead exposed worker, no report about the relation between blood lead levels and BAEP in preschool children. The purpose of this study is to detect BAEP in preschool children with different blood lead levels, and to understand the concrete position and extent of effects of lead on the auditory nerve or brainstem of auditory pathway. Subjects and MethodsOne hundred and fourteen asymptomatic subjects, including 80 males and 34 females, were enrolled in this study, and their age ranged from 1 to 7 years (Mean盨D: 3.46 + 1.56). They were divided into 2 subgroups according to their blood lead levels (PbB): low lead subgroup (PbB<10ug/dl) and high leadsubgroup (PbB>10ug/dl). The age and gender of two subgroups had no significant differences. The blood lead levels were assessed by graphite furnace atomic absorption spectroscopy. The standardized specimens were provided by the Centers of Disease Control (CDC), USA. Both bench and blind quality control specimens were used.BAEP were recorded with the subjects reclining on bed in a dimly lit and quiet room. Four electrodes were placed on the forehead (FPz), the vertex (Cz) and each mastoid (Ml, M2). Electrodes impedance was maintained below 5 KOhms. Monaural stimulation with 75 dB (nHL) broadband rarefactions clicks at a rate of 1 1.4/second was given with headphones, while contralateral ear was given 35dB (nHL) white noise. Responses were amplified and averaged 2000 times and every ear was repeated 2 times. Average values were calculated for peak latency (PL), interpeak latency (IPL), interaural latency difference (ILD), amplitude (Amp), and the ratio of amplitude of peak V and amplitude of peak I (AmpV/ 1).PbB were converted to nature logarithms (In(PbB)) because they showed a positive skewness distribution. Significance of differences between subgroups were calculated using unpaired T-test. To excluded the effects of age and gender, part coefficient between In(PbB) and BAEPs components were calculated. The relationship between BAEPs components and In(PbB), age, gender (treating female as 0 and male as 1) was examined using stepwise multiple linear regression analysis. A two tailed P value less than 0.05 were considered significant. ResultsThe PbB of 114 subjects ranged from 3.2ug/dl to 38.0ug/dl with a positive skewness distribution. The median of PbB was Q-O^g/dl and arithmetic average level was 8.80ng/dl (standard deviation 1.61ug/dl). Among them, 43.0%(49/114) were equal to or over 10u,g/dl and 3.51%(4/114) were over 20ug/dl.The BAEP of all subjects had no obvious abnormalities in morphology and3 main peaks (I, III and V peak) differentiated clear.According to univariate analysis, significantly longer PL I and V were found in high lead subgroups in both ears (PO.05) and significantly longer PL III was just found in left ear (PO.05). After excluding the effects of age and gender as confounding factors, statistically significant and positive correlations were found between In(PbB) and bilateral PL I, V, III of left ear (P<0.05). A significant and positive correlation was also found between In(PbB) and PL I of left ear even in low lead subgroup (P>0.05).The results of stepwise multiple linear regression analysis showed that PL I had a significant and positive correlation with In(PbB) (P<0.05) but no significant correlation with age or gender were found (P>0.05). Correlations of PL III, V, and gender and age were...
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